(a) Field of the Invention
This invention relates to cyclic alkylidenyl N-(pyridazinyl)aminomethylenemalonate derivatives useful as schistosomicidal agents, to processes for their preparation and to compositions and a method for their use.
(B) Description of the Prior Art
The Sterling Drug Inc. Lesher U.S. Pat. No. 3,563,981, issued Feb. 16, 1971, discloses cyclic alkylidenyl N-Ar-aminomethylenemalonates to be useful as intermediates for preparing cyclized products, in turn, useful as intermediates for preparing antimalarials and anti-inflammatory agents. Also, said patent shows the cyclic alkylidenyl N-Ar-aminomethylenemalonates to have antiviral activity, e.g., against vaccinia virus in mice, and to be prepared by reacting an aromatic amine, Ar-NH.sub.2, with a mixture of a trialkyl orthoformate and a cyclic alkylidenyl malonate. The patent defines "Ar" as "1-2 ringed aryl," that is, meaning "aromatic radicals having one or two aromatic rings which can be benzenoid or five- or six-membered heteroaromatic", including, inter alia, phenyl, naphthyl, pyridyl, quinolyl, pyridazinyl, etc. Preferred embodiments are the compounds where Ar is phenyl and substituted-phenyl, the latter having from one to three substituents illustrated, inter alia, by lower-alkyl, halo, nitro, amino, lower-alkylamino, lower-alkanoylamino, etc. This patent discloses at lines 30-35 of column 2 that the other said 1-2 ringed aryl radicals, e.g., inter alia, pyridazinyl, also can bear at available ring-carbon positions substituents such as those illustrated for the benzene ring of phenyl. The only specifically characterized compound where Ar is a pyridazinyl moiety is cyclic isopropylidenyl N-(6-methoxy-3-pyridazinyl)aminomethylenemalonate shown in the paragraph at lines 47-52 of column 29. Claim 18 defines isopropylidene 3-pyridazinylaminomethylenemalonate (same as cyclic isopropylidenyl N-(3-pyridazinyl)aminomethylenemalonate).